How to Convert the bellow query Sql to oracle

DECLARE @DateFrom DATETIME,@DateTo DATETIME

DECLARE @Dates NVARCHAR(2000), @Buckets NVARCHAR(2000)

set @Dates ='10-Mar-2015,15-Mar-2015,25-Apr-2015'

set @Buckets ='0-30,31-60,61-90'

Declare @Start_Bucket int, @End_Bucket int

select TOP 1 @DateFrom= IDField from dbo.FN_SPLIT(@Dates,',')

Order By CAST(IDField aS DATETIME)

select TOP 1 @DateTo= IDField from dbo.FN_SPLIT(@Dates,',')

Order By CAST(IDField aS DATETIME) desc

if (DATEPART(day, @DateTo)=25)

BEGIN

SELECT @DateTo=DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,@DateTo)+1,0))

END

Set @Buckets=REPLACE(@Buckets,'''','')

SELECT @Start_Bucket=

SUBSTRING(SUBSTRING(@Buckets,0 ,CHARINDEX(',', @Buckets)),0,

CHARINDEX('-', SUBSTRING(@Buckets,0 ,CHARINDEX(',', @Buckets))))

if CHARINDEX('-',(reverse(left(reverse(@Buckets), charindex(',', reverse(@Buckets)) -1)) ))!=0

BEGIN

SELECT @End_Bucket=

SUBSTRING(reverse(left(reverse(@Buckets), charindex(',', reverse(@Buckets)) -1)),

CHARINDEX('-',reverse(left(reverse(@Buckets), charindex(',', reverse(@Buckets)) -1)))+1,

LEN(reverse(left(reverse(@Buckets), charindex(',', reverse(@Buckets)) -1))) )

END

PRINT @DateFrom

PRINT @DateTo

PRINT @Start_Bucket

PRINT @End_Bucket